Kyu-Chan Lee

Design and analysis of automotive high intensity discharge lamp ballast using micro controller unit

A new scheme of the automotive high intensity discharge (HID) lamp ballast systems is proposed. The proposed scheme is consisted of the high frequency DC-DC converter and the low frequency DC-AC inverter as same as conventional HID ballast system. However this system separates the input voltage of the ignitor from DC link voltage using auxiliary winding, which results in the use of the lower voltage rating power devices for HID lamp ballast system compared with conventional system. As a result, proposed system has a lower cost or a higher efficiency. For the improvement of the efficiency, the proposed ballast controller using micro-controller unit (MCU), controls the frequency to operate the DC-DC converter in critical conduction mode. This paper presents the design and analysis of the proposed ballast and some experimental results.

A New DC Anti-Islanding Technique of Electrolytic Capacitor-Less Photovoltaic Interface in DC Distribution Systems

This paper proposes a photovoltaic (PV) generation system interfaced with a dc distribution system. DC interface allows for the improvement of system efficiency by fully utilizing dc-based renewable sources and storage devices. In this paper, issues on PV interface for dc distribution systems are discussed for energy-efficient and reliable system implementation. AC and dc PV interfaces are mathematically analyzed. In dc distribution, eliminating electrolytic capacitors in PV interfaces improves system reliability, increases system efficiency, and reduces cost. In addition, this paper proposes a new anti-islanding technique for dc distribution as a system protection scheme. The operating principle is presented in detail and analysis shows that the proposed injected current perturbation technique is an effective solution for anti-islanding operation. A prototype converter features a simple structure with no electrolytic capacitor, which ensures a longer lifetime of the PV power circuit. Experimental results of the prototype circuit show a maximum efficiency of 98.1% and a European efficiency of 97.5%. The proposed anti-islanding technique shows fast response to the islanding condition in less than 0.2 s. It also shows that the average maximum power point tracking efficiency is 99.9% in normal conditions, which verifies the performance of the proposed scheme.

Analysis of Current Distribution in Driving Multiple Cold Cathode Fluorescent Lamps (CCFL)

Cold cathode fluorescent lamps (CCFLs) show complex characteristics, which make it difficult to drive them in parallel. In this paper, a backlight inverter, which can drive multiple CCFLs using single controller and single switching network, is presented. The analysis of the lamp current distribution is presented in detail. The current-balancing condition, under which the lamp currents are well balanced in the presence of the lamp voltage variation, is derived. The effect of the resonant component variation is also investigated. The analysis results are verified from experiments with two 720-mm/4-mm CCFLs for 32-in liquid crystal display televisions. Experimental results with eight CCFLs are also presented in the presence of the lamp voltage and the resonant component deviation

A fuzzy current controller for field-oriented controlled induction machine by fuzzy rule

The authors propose a fuzzy, current-controlled, pulse-width modulation (PWM) which minimizes current ripple using fuzzy set theory at a constant switching frequency. This technique is applied to an electrical drive system with an induction motor and studied by simulation. The results show that the technique performs better than classical methods such as ramp comparison and the hysteresis band control method.<<ETX>>

Digitally Controlled Current Sensorless Photovoltaic Micro-Converter for DC Distribution

In this paper, a digitally controlled photovoltaic (PV) micro-converter for dc distribution with sensing no current is presented. Current information for maximum power point tracking (MPPT) is estimated from system parameters, which leads to reducing power losses caused in sensing current and the number of components. Operation analysis of boundary conduction, quasiresonant, and discontinuous conduction modes is presented for its implementation. The high current estimation accuracy not only allows adaptive operation mode changes for efficiency optimization, but also guarantees achievement of high MPPT efficiency. Loss analysis of each operation mode is also presented to determine optimal transition points for mode change. A prototype PV micro-converter for a 120-W PV module is implemented by utilizing a digital signal processor. Experimental results verify that the proposed method is stable in both static and dynamic operations. European efficiency and MPPT efficiency are measured higher than 97.5% and 99.5%, respectively.

Transient current suppression scheme for bi-directional DC-DC converters in 42 V automotive power systems

42 V electrical power systems are on their way to replacing the present 14 V systems in automobiles and 42 V/14 V dual voltage systems have been proposed to provide backward compatibility with the existing components for the 14 V system. The synchronous buck/boost converter is an attractive topology for 42 V/14 V dual voltage systems since it offers bi-directional operation without additional components. In this paper, transient currents generated during converter startup or changes in operation modes between buck and boost are analyzed and a cost effective solution to remove the transient currents is proposed. The validity of the proposed control strategy is investigated through simulations and experiments

Design of fluorescent lamp ballast with PFC using a power piezoelectric transformer

An investigation of a high power piezoelectric transformer as a potential component for a fluorescent lamp ballast with power factor correction (PFC) is discussed. The attractiveness of the piezoelectric transformer is primarily the simplicity of the resulting circuit, and it is easy to produce in mass with a low cost. Electrical modeling, considering operating current level and analysis of the piezoelectric transformer are performed through measurements to design a fluorescent lamp ballast with a single stage charge pump PFC. The experimental and simulation results are provided to verify theoretical analysis.

Arc protection scheme for DC distribution systems with photovoltaic generation

This paper presents a dc arc protection scheme for a dc distribution system. The location of arc fault detectors (AFD) and interrupting devices (ID) for system safety guarantee is discussed. Through the proposed scheme, the dc distribution system is protected from arc faults occurring in photovoltaic (PV) sources and load sides. Operation principle is discussed in detail. Experimental results verify the feasibility of the protection scheme.

Modeling of CCFL using lamp delay and stability analysis of backlight inverter for large size LCD TV

Cold cathode fluorescent lamps (CCFL) for LCD TVs have a special v-i characteristic, which can make the backlight inverter system unstable. In this paper, modeling of both the cold cathode fluorescent lamp and the backlight inverter is performed in terms of incremental impedance in the frequency domain. The stability analysis of the backlight inverter and the CCFL is presented using the derived models. It is concluded that the time delay, after which the lamp voltage responds to the lamp current change, contributes to the incremental impedance of the CCFL at the high frequency region, which may cause instability of the backlight inverter. The time delay is considered as a lamp characteristic. The effect of the inverter design parameters on the stability is also investigated. The lamp model and the stability analysis results are verified from experiments with a backlight inverter for 32-inch LCD TVs.

Power factor correction converter using delay control

A low cost universal input voltage single-controller power factor correction converter for a 200 W power supply is proposed. It consists of the PFC part followed by a DC-DC converter as in a conventional two-stage scheme. However a single PWM controller is used as in a single-stage PFC scheme. The switch in the PFC part is synchronized with the switch in the DC-DC converter and has a fixed frequency. Employing an adaptive delay scheme, the PPC switch is controlled to limit the capacitor voltage within a desired range for optimum efficiency and to reduce input current harmonic distortion. The design procedures of the delay scheme, the feedback loop, and experimented results are presented to verify the performance.